In recent years, modules for optical apparatuses that are to be installed in optical apparatuses, such as digital cameras and mobile phones with camera functions, have been developed (for example, Japanese Unexamined Patent Publication No. 2002-182270 (publication date: Jun. 26, 2002)).
The following explains, as an exemplary conventional module for an optical apparatus, which module includes a solid-state image sensor, such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor) imager, and a camera module 120 taught in Japanese Unexamined Patent Publication No. 2002-182270, with reference to FIG. 7. FIG. 7 is a sectional view showing a structure of the camera module 120.
As shown in FIG. 7, the module 120 for an optical apparatus includes a wiring board 106 and conductor wirings 110, which are formed on both surfaces of the wiring board 106. The conductor wirings 110 are suitably connected to each other inside of the wiring board 106. An image processing apparatus 104 is bonded to the wiring board 106 by die-bonding via a die-bonding material 107. A connection terminal 109 of the image processing apparatus 104 is electrically connected to the conductor wirings 110 via a bonding wire 112. Further, a chip component 113 is mounted on the wiring board 106.
Further, a spacer chip 102 is bonded to the image processing apparatus 104 via an insulative bonding agent 105. A solid-state image sensor 101 is bonded to a plane surface of the spacer chip 102 via an insulative bonding agent 103. Further, a transparent cover section 114 is provided above the solid-state image sensor 101.
In this conventional structure, every connection terminals of the image processing apparatus 104 and every connection terminals of the solid-state image sensor 101 are electrically connected to the conductor wirings 110 via the bonding wire 111 or the bonding wire 112. This requires a space for the bonding wires 111-112 and the conductor wirings 110, which are to be connected to the wires 111-112, causing the module to increase in size.
Further, with the conventional structure, there arises a problem that an optical distance from the lens 115 to the solid-state image sensor 101 does not correspond to a focal length f of the lens 115 due variations, such as warping and deflection, occurred during the steps of producing the wiring board 106 or after the wiring board 106 is mounted.
FIG. 8 is a diagram showing an example of such defects. The figure shows a case in which a central section of the wiring board 106 is protruded. As shown in FIG. 8, the lens 115, the central section of the wiring board 106, and the solid-state image sensor 101, which is provided at the central section of the wiring board 106, are maintained parallel to one another, but both ends of the wiring board 106 are depressed with respect to the center. Accordingly, a lens-holder main-body 117 bonded to the wiring board 106 moves downward with respect to the central section of the wiring board 106. In other words, a reference for positioning the lens 115 moves downward. As a result, the optical distance from the lens 115 to the solid-state image sensor 101 becomes f−Δf (Δf indicates an amount of change in the thickness of the wiring board 106), diverging from the focal length f of the lens 115.
In this case, a focus adjuster 116 is rotated to adjust the optical distance, which is from the lens 115 to the solid-state image sensor 101, to the focal length f of the lens 115, thereby making the optical distance correspond to the focal length f of the lens 115. In other words, adjustment is made by Δf with the focus adjuster 116 to bring the solid-state image sensor 101 into a position that is away from the lens 115 by the focal length f.
As discussed above, in the conventional module for an optical apparatus, the lens-holder main body 117 is bonded to the wiring board 106 by using the wiring board 106 as a reference for positioning the lens 115. Hence, the optical distance from the lens 115 to the solid-state image sensor 101 sometimes differs from the focal length f of the lens 115 due variations, such as warping and deflection, in the wiring board 106.
This necessitates adjusting the optical distance, which is from the lens 115 to the solid-state image sensor 101, to the focal length f of the lens 115, with respect to every modules. This requires expensive equipments and workers. Further, this adjustment requires a skilled worker. Furthermore, the lens holder requires two mechanical components, the lens-holder main body 117 and the focus adjuster 116. It has been structurally difficult to decrease the size of the lens holder and therefore the size of the module. Further, being mechanical components, the components are difficult to manufacture on mass-production basis. Hence, the proportion of production costs of the lens holder with respect to production costs of the module is high. This causes the production costs to increase.
In view of the foregoing, there has been suggested a module for an optical apparatus to solve the problem of increase in size of the module and the problem of deviation in the focal length. For example, the module taught in Japanese Unexamined Patent Publication No. 2005-216970 (publication date: Aug. 11, 2005) (U.S. patent application publication No. 2005/0163016 (publication date: Jul. 28, 2005)) includes (a) a bonding section to bond a transparent cover section to a solid-state image sensor and (b) a coupling section to connect the transparent cover section and an optical-path defining unit, and the solid-state image sensor includes a through electrode, thereby decreasing the size of the module.
The following explains a module 220 for an optical apparatus that is taught in Japanese Unexamined Patent Publication No. 2005-216970, with reference to FIG. 9. FIG. 9 is a sectional view showing a structure of the module 220.
As shown in FIG. 9, the module 220 includes a solid-state image sensor 201, an image processing apparatus 202, a wiring board 203, and an optical-path defining unit 212, which defines an optical path to an effective pixel area 200 formed on the solid-state image sensor 201.
A pattern of the conductor wiring 204 is formed on both surfaces of the wiring board 203. The conductor wirings 204 are suitably connected to each other inside of the wiring board 203. The solid-state image sensor 201 includes a through electrode 207. The image forming apparatus 202 includes a through electrode 208. A rear surface of the solid-state image sensor 201 and a front surface (flat surface section) of the image processing apparatus 202 are bonded together with a bonding section 205. The through electrode 207 of the solid-state image sensor 201 and the through electrode 208 of the image processing apparatus 202 are electrically connected to each other.
Further, a rear surface of the image processing apparatus 202 and a front surface of the wiring board 203 are bonded together with a bonding section 206. The through electrode 208 of the image processing apparatus 202 and the conductor wiring 204 formed on the front surface of the wiring board 203 are electrically connected to each other.
With this structure, no space for the bonding wires to be provided is necessary in a laminate of the solid-state image sensor 201, the image processing apparatus 202, and the wiring board 203. This allows the module 220 to be reduced in size. For example, a distance from an edge section of the solid-state image sensor 201 to an inner wall of the optical-path defining unit 212 decreases, so that the size of the module 220 decreases.
The optical-path defining unit 212 is coupled with a transparent cover section 210 via a coupling section 213. The transparent cover section 210 is bonded, with a bonding agent 209, to a surface of the solid-state image sensor 201, on which surface the effective pixel area 200 is formed. The optical-path defining unit 212 holds a lens 211 on its internal surface at one end of one opening, in a manner such that the lens 211 faces the effective pixel area 200 of the solid-state image sensor 201 via the transparent cover section 210.
The other end of the optical-path defining unit 212 is coupled with the wiring board 203 via an adjustment section 214 formed of a bonding agent that maintains some flexibility even after being cured.
In this case, the optical distance from the lens 211 to the solid-state image sensor 201 is not affected by warping, deflection, or the like in the wiring board 203. Therefore, if the optical distance is designed in such a way as to match the focal length f of the lens 211, then the optical distance always matches the focal length f. This makes it unnecessary to adjust the optical distance to the focal length f of the lens 211. Accordingly, expensive equipments and workers for adjustment are become unnecessary, allowing significant reduction in costs.
However, in the module of Japanese Unexamined Patent Publication No. 2005-216970, although the optical-path defining unit 212 and the wiring board 203 are bonded together with the adjustment section 214, the solid-state image sensor 201, the image processing apparatus 202, and the transparent cover section 210 are squeezed in a space surrounded by the optical-path defining unit 212 and the wiring board 203. This causes defects such as overall distortion and partial breakage in the module.
Further, as the modules for optical apparatuses have been installed in portable devices widely in recent years, a smaller and lighter module has been demanded.